A Deep Dive into Hydration and Resumability

In the dynamic world of web development, the drive for better performance has led to significant changes in how we build and deliver web applications. This article explores the evolution from past methods to current practices, and how new technologies like “resumability” are shaping the future. We will refer to visual comparisons to better understand these concepts.

The Past: Separate Rendering and Interactivity

In the early days of web development, rendering and interactivity were handled separately. Server-side technologies such as PHP and Ruby on Rails were used to render HTML, while client-side interactivity was achieved with libraries like jQuery.

Separate Rendering and Interactivity:

• HTML rendering was done on the server.
• Interactivity was added later on the client.

Technologies Used:

• Rendering: PHP, Rails.
• Interactivity: jQuery.

Performance:

• Advantages: Efficient rendering.
• Disadvantages: Slower development cycles, higher error rates, duplicated logic.

This separation often led to inefficiencies and inconsistencies, making the development process cumbersome and error-prone.

Current State: Unified Frameworks with Hydration

Modern web development has moved towards unified frameworks that combine rendering and interactivity. Popular frameworks like Angular, Vue, Svelte, and React exemplify this approach.

Unified Frameworks:

• Rendering and interactivity are managed within a single framework.

Application Lifecycle:

• The application runs twice: once on the server to render the initial HTML, and again on the client to add interactivity.
• This process is known as hydration, where the client-side JavaScript re-renders the server-rendered HTML.

Technologies Used:

• Angular, Vue, Svelte, React.

Advantages:

• Unified development model.
• Faster development cycles.
• Scalability with increased complexity.

Disadvantages:

• Slower startup performance due to the need to re-render the application on the client.
• Redundant data transmission, as both HTML and JavaScript carry the application’s state.

While hydration improves user experience by making pages interactive quickly, the initial load time can still be slow, particularly on mobile devices and slow networks.

The Future: Resumability

As the quest for performance continues, a new approach known as “resumability” is emerging. This method aims to significantly enhance startup performance by minimizing redundant processes.

Resumability:

• The application runs only once, primarily on the server, with minimal JavaScript execution on the client.

Application Lifecycle:

• HTML and a small amount of JavaScript are sent to the client, making the page instantly interactive.
• The full application state is not duplicated; instead, it resumes from the server-rendered state.

Technologies Used:

• Google Wiz, Qwik, Marko V6, Astro JS.

Advantages:

• Faster initial interactivity.
• Reduced data transmission, as the duplication of application state is eliminated.
• Consistent startup performance regardless of page complexity.

Disadvantages:

• New approach may require adaptation and learning for developers accustomed to traditional hydration methods.

Resumability addresses the drawbacks of hydration by ensuring that only essential interactivity code is executed on the client, leading to significantly faster startup times.

Comparison of Architectures

To better understand the differences between these approaches, here’s a comparison:

Aspect	Past (Separate)	Current (Hydration)	Future (Resumability)
Rendering	Server-side	Server-side & Client-side	Primarily Server-side
Interactivity	Client-side	Unified in Framework	Minimal Client-side
Initial Load Time	Fast	Slower due to hydration	Fast
Data Transmission	Less	Redundant	Reduced
Development Complexity	Higher	Moderate	Lower
User Experience	Inconsistent	Improved	Optimal

Conclusion

The evolution from separate rendering and interactivity to unified frameworks and now towards resumability highlights the ongoing efforts to optimize web performance. Hydration has played a crucial role in enhancing user experience, but resumability promises to set a new benchmark for startup performance.

As web development continues to evolve, embracing these new technologies will be key to building faster, more efficient web applications that provide seamless experiences for users across all devices and network conditions. The future of web development is undeniably performance-centric, and frameworks like Google Wiz, Qwik, Marko V6, and Astro JS are leading the way.

Understanding and leveraging these advancements will be essential for developers aiming to stay ahead in this fast-paced digital landscape.